The GR Type 1863 Megohmmeter was introduced in Catalog U (1970). It is still available from IET Labs as of 2024. Specifications. Test Voltage: 50, 100, 100, 250, or 500 V; 5 mA limit; Resistance Range: 50 kΩ 20 20 TΩ in 7 ranges; Links. The Type 1864 Megohmmeter is similar but with a 200 TΩ top range, and test voltage variable from 10 V to ...